In known conductor-line systems, movable devices such as, e.g., cable trolleys or transport gears of an electric telpherage system with or without electric loads, travel along a conductor line. In order to supply the device with electric energy, said device is provided with a collector, the sliding contacts of which engage into conductor lanes extending along the conductor line. The devices may consist, e.g., of transport gears or cable trolleys that move along rails, wherein said devices are equipped with an electric drive that is supplied with electric energy via the conductor line. Several transport gears may also be coupled to one another, in which case only the front transport gear is frequently equipped with an electric drive. The other transport gears, in contrast, merely serve as load carriers and do not feature a drive or other electric loads.
One example of a known conductor-line system of this type is disclosed in DE 196 47 336 A1. In this case, a collector trolley is provided that moves along an installation section on an independent running rail, wherein sliding contacts engage into conductor lanes of the conductor line that are realized in the form of current rails.
In order to protect the operating personnel and other devices, the transport gears or their usually metallic housing and other parts that should not conduct a current are grounded. For this purpose, a protective sliding contact is provided that engages into a neutral and grounded protective-conductor lane of the conductor line that is realized in the form of a protective conductor. The other conductor lanes are phase conductors that are energized in the normal operating mode and deliver a current to the electric loads. Trailing transport gears without electric loads are usually also connected to the protective-conductor lane via a protective sliding contact. In case of a fault, in which parts or the housing of the transport gear are energized, this ensures that the phase conductor voltage is switched off as quickly as possible, for example by means of a fault current detection, before a person or other system components are energized.
The sliding contacts of the collectors are frequently designed for clicking or clipping into the conductor lanes in order to transfer the sliding contacts from an idle, non-contacting position into a contacting position on the conductor lane. This is usually realized manually by means of an operator. Due to the frequently poor accessibility to the sliding contacts or the inattention and carelessness of the operator, it may occur that a sliding contact is not clipped into the intended conductor lane, but rather into a phase-conductor lane situated adjacent thereto. This is particularly dangerous if the protective sliding contact is not clipped into the protective-conductor lane, but rather into one of the phase-conductor lanes such that all parts of the transport gear that are not intended for conducting a current and normally grounded and therefore not energized by means of the protective-conductor lane or the housing of the transport gear are energized or become energized when the phase conductor voltage is switched on. This represents a significant risk for the operating personnel and system components, particularly if no fault detection is provided that detects such a fault and sounds an alarm. For example, an operator contacting the energized components may receive a possibly fatal electric shock.
This risk is particularly high when clipping in the protective sliding contact of trailing trolleys without electric loads because they do not feature additional sliding contacts for the phase-conductor lanes. If the protective sliding contact is accidentally clipped into a phase-conductor lane in this case, the trailing trolleys or their housing is energized with the operating voltage. If the correct connection between the protective sliding contact and the protective-conductor lane is not checked again, the potential risk is particularly high because such an error is frequently not detected at all over extended periods of time or until an accident occurs.
In order to lower this risk, JP 08 072 593 A proposes to provide colored marking to the lateral lines of the ground conductor in a conductor line with three conductors for the electric energy supply and one ground conductor. This solution, in principle, improves the protection against clipping a ground-conductor collector contact into an energy-supply conductor because the operating personnel is able to better distinguish the ground conductor from the energy-supply conductors. However, it is still possible to erroneously connect the ground-conductor collector contact to one of the energy-supply conductors in this case such that the risk of an operating error can never be reliably precluded.